This invention relates to a catheter for introduction into body cavities which is made out of a high molecular material, for example plastic or latex, and a physiologically compatible external rigidizing coating. The word catheter as used herein is to be understood in its general meaning and embraces, for example catheters, vein-catheters and similar products.
Two different and by themselves contradictory demands are important for such catheters. On the one hand they must be sufficiently stiff for the introduction into the body cavity in order to have such procedure easily effected. That is particularly important when the patient is not capable to aid the introduction by swallowing motions or also when the introduction must be handled against reflex motions of the body. On the other hand the catheter must be soft and flexible when introduced, because it must dwell within the patient for extended periods on some occasions and should not incommodate or prevent the patient from moving freely. When such catheters remain several days in the stomach or in the duodenum or in other body cavities, they should not become hard due to the loss of softeners, because that would lead to pressure necroses.
Known soft-vinyl catheters presently used do not fulfil the last mentioned requirement. Such PVC-catheters are cooled prior to introduction (see, for instance German DE-AS 21 40 994) in order to increase temporarily their rigidity. On the other hand catheters made out of highly elastic materials are known, for example made from silicone rubber or latex, which are tolerated by patients with relative ease for even long dwelling times. For these catheters, however, the introduction is rather problematical. Therefore, a rigidizing element is provided or introduced in the catheter, a wire for instance, which is removed from the catheter once it is introduced into the body cavity sufficiently. It is disadvantageous, however, that the introduction of the wire necessitates painstaking manipulations and furthermore, the danger exists that the wire might puncture the thin catheter wall and that internal injuries of the patient might result. Furthermore, the aforementioned German DE-AS 21 40 994 also discloses that the catheter itself be provided with a coating of silicone resin or fluorocarbon resin but which serves mainly to increase the compatibility with the body and to prevent eventual toxic reactions.